What is a CAE?
Energy Savings Certificates, known in Spain as Certificados de Ahorro Energético or CAEs, are a practical way to turn verified energy savings into economic value. A CAE is an official electronic certificate that proves an energy efficiency action has delivered a new saving in final energy, and the unit is simple: one CAE equals one kilowatt hour of annual savings. The system creates a regulated market where energy suppliers with annual savings obligations can meet those obligations by acquiring CAEs, rather than relying only on contributions to the National Energy Efficiency Fund. In short, the CAE system makes energy savings measurable, verifiable, and tradable, helping accelerate energy efficiency investment across the economy.
Why CAEs matter for public sector renovations
For municipalities and public institutions, CAEs are much more than administration. They can unlock an additional revenue stream linked directly to the impact of a renovation. When a public building upgrades lighting, improves insulation, or modernises heating and cooling, the resulting verified savings can be converted into CAEs and transferred to an obligated or delegated party in exchange for a financial consideration. This improves project economics and can help public budgets go further, especially when combined with solid project planning and documentation from day one.
How CAEs help finance energy efficiency
The financing logic is straightforward. First, an efficiency measure is implemented. Then the savings are calculated and verified by an accredited verifier. After that, the file is reviewed and the CAEs are issued through the administrative pathway, and finally they can be traded and settled by the obligated parties. Because the process includes verification and public validation steps, CAEs bring credibility to the claimed savings, which is exactly why they can be monetised.
Steps for public entities
For public bodies, the most common approach is to work with a delegated or obligated party and formalise the transfer of savings through a CAE agreement. In practice, delays usually appear when any of the required steps has to be repeated or clarified, especially around evidence and consistency. The process includes execution of the measure, independent verification, submission of the request, validation and CAE issuance, and then trading and settlement. If documentation is incomplete, inconsistent with the selected measure, or missing key proof of implementation, it can trigger back and forth during verification or administrative validation. Separately, delays can also arise if roles and ownership are not crystal clear in the CAE agreement, because the system relies on a formal transfer of the savings from the owner to the obligated or delegated party.
Incompatibilities to watch
This point is indeed one of the most interesting parts of the system because it sits at the intersection of public funding rules and a market mechanism. The general rule is that CAEs can be compatible with public aid programmes, with a key exception: compatibility is not allowed when the support is financed with charge to the National Energy Efficiency Fund, as referenced in the framework for the system. This means the question is often not “Is there a grant?” but “Where does the grant funding come from?” and whether the same savings would be counted twice. In parallel, ownership and exclusivity matter. A CAE agreement is explicitly about the owner of the energy savings transferring those savings to an obligated or delegated party in exchange for compensation, so contracts must clearly state who owns the savings and who has the right to claim them. In practice, this is especially relevant in public sector projects delivered through ESCO models or third parties, where the contract must avoid overlapping rights.
Why this matters now
In the LEVERAGE Accelerator, the goal is not only to help public bodies design strong renovation projects, but also to make them easier to finance by connecting them with the right private finance partners and providing practical support to shape “investment ready” proposals. In that context, CAEs can play a very concrete role as a bridge between technical impact and financial attractiveness: they translate verified energy savings into an additional value stream that can strengthen a project’s business case and reduce the funding gap that municipalities often face.
What the Accelerator brings, and what many standalone CAE discussions miss, is integration. Instead of treating CAEs as an afterthought, LEVERAGE can help municipalities consider them early, position them alongside other funding options, and ensure they are reflected coherently in the overall financing narrative that is presented to the market. Just as importantly, the Accelerator can help make sure the basics are clear from the start, especially around compatibility with other funding sources and the ownership of savings when third parties are involved, so that value is not lost later due to avoidable contractual or administrative friction.